As the number of patients in need of heart transplants has grown, surgeons have gotten pickier about the organs they're willing to use, a new study finds.

In 1995, 44% of available hearts ultimately found their way into new bodies, according to data from the Organ Procurement and Transplantation Network. By 2006, that figure had dropped to 29%. As of 2010, it had rebounded somewhat to 32%, according to the study published this week in the American Jou...